Timing circuit



e, D. HANCHETT, JR

TIMING CIRCUIT Filed April 50, '1943 IVENTOR Patented Dec. 13, 1949 TIMING CIRCUIT GeorgeDi Hanchett, Jr, Millburn, N. J assignor toRadioCorporation of America, a corporation.

of'Ilelaware ApplicationApriLKO, 1948, Serial N 0. 24,331

10. Claims. (Cl. 315-218) My invention. relates: to. electronic circuits and particularlytorcircuitsjin which a-recurrent eventv must bear' a time. relationship to a previous;

cyclically recurrent event where the-time. interval between events is a function of the frequency of recurrence of the firstevent.

For purposes. of illustration, I have shown myinvention as applied to an ignition system of an internal combustion engine in which the firing of the spark inthe cylinder hears a timerelat-ionship to the speed of the-engine.

In an; internal combustion engine, maximum fuelemciency at givenspeedris obtained when the spark occurs ata definitepoint in the stroke of the piston, but with changes.- in speed,- the firing point of maximum eificiency isat difierent positions of the piston, wherein the firing point occurs earlier in the compression stroke. as the engine speed increases.

Heretofore, in internal combustion engines, it has been necessaryto select a point of firing that will be the same for all speeds, but most efficient. at a predetermined speed whichis generally in.

the middle range of speeds of. which such. engine is capable, or, in lieu thereof, to provide elaborate and complicated mechanical linkages. for automatically or manually adjusting the sparktime.

These expedients have not proven entirely satis factory in that they present additional moving.

parts which are subject to failure through. wear and breakage.

In addition to the foregoing, previousignition systems necessarily included other mechanisms, suchas. cam actuated relays and mechanically operated distributors, in the production and distribution of the sparkproducing pulses. These mechanisms are also subject. to mechanical and electrical failure.

Another objectionto the ignition systems now in useis that. electrical disturbances are set up inthe long high-tension conductors forming a part-ofsuchsystemawhich disturbances are reflected in any radio equipment that may be present, unless special care is takento filter such disturbances. from. the equipment.

Accordingly, it.is an object of my invention to provide. an. electrical. circuit in which the time relationship between two series. of events is automatically adjusted-without the use of mechanical linkages to efiect the adjustment where the time interval between such series is a function-of the frequency of recurrence of the events in the first series.

Another object of. my inventionis to provide an electrical circuit that is adaptable to ignition system. for internal combustion; engines wherein the time relationship between two series of? cyclically recurrent events is automatically-- ads usted. without the, use of mechanical linkages-to effect the adjustment. Inaccordance withthe illustration I have chosen, the first series of events mentioned above would be thestroke; of"

the. piston or a part of the engine moving at a; speed proportional to the stroke of the piston,. The second series,

for example, the camshaft. of events would. be the firing of the spark in th cylinder.

Stillanother object of my invention is theprov vision of an electrical circuit that is suitable:- f r ignition system: in which. there; are no. movin parts that. aressubjiectito mechanical failure.

It isa further. object. of my invention to provide. a. circuit. of. the; type. mentioned in which all high. tension. conductors. or elements occupy asmall space. and may be. completely enclosed or shielded: to. reduce radio interference to anegligible; amount.

In. accomplishingthese obj cts, I have provided anelectrical pulse generator which consists oi'a pick-up-coil: closely associated with asmall high quality, permanent magnet which is; rigidlymounted. on some cyclically moving part from which-the time reference is to be taken, as on the. cam shaft of an internal combustion engine; The-pulses, thus produced are used to trigger a gas discharge tube which, acts as a gate for the current: flowing through a suitable load device which, in my; illustration, would be the ignition transformer. Between the pulse generator and. the tube, Ihave provided a pulse sharpening circuit to give. amore-positive control, and an. electrical phase shifter which is responsive to the frequencyof the pulses produced at the generator, to give the automatic. time relation betweenthe two series of-events asa function of the frequency of recurrenceroi the events in the first series.

A better understanding of my invention may be; had from the following description taken in conjunction with theaccompanying drawing in which the single figure schematically represents an embodiment of my invention.

Referring to the figure, there has been provided apermanent magnet l, rigidly securedto a. cyclically moving part, such as the cam shaft 2 of an internal combustion engine. Closely associated with the magnet. is a pick-up coil 3-, connected to asimple pulse sharpening circuit 4, whichmay be of the well-known simple resistance-capacitance type. One line from the pulse sharpening device is grounded and the other line is connected through a capacitor 5 and a grid resistor T, to the control grid of a gas discharge tube 8, the cathode of which is grounded. A second resistor 6 is connected between the point of junction of the capacitor 5 and the grid resistor 1, and the oathode of the gas discharge tube through its cathode heater. The anode of the tube is connected through a suitable load device, which in the illustrated example is the primary of an ignition transformer 9 and a capacitor H, and thence to ground. The junction between the load device and the capacitor II is connected through a resistor l2 and an anode supply battery l3, to ground. In the example selected, the terminals of the secondary of the transformer 9 are connected directly to a spark gap l0.

In operation, the system functions as follows:

The cyclically moving part, which is represented by the cam shaft 2, periodically carries the changing magnetic field caused by the motion of the magnet induces pulses of electrical energy in' the coil. The pulses thus produced are passed through, the pulse sharpening circuit 4, where their shape is modified to produce pulses with a steep leading edge thus providing more accurate time control. The pulses are then passed through the capacitor 5 and grid resistor l to the control of the gas discharge tube 8, causing it to become conductive, since it had been conditioned to be ready to fire at this time by the charging of the capacitor H by the battery l3, through the resistor 12, while the tube was in the non-conducting state.

This action of the tube is due to the characteristics of a gas discharge tube wherein the tube is. conditioned to conduct when the anode potential is at a fixed level above the potential of the cathode, but the firing is restrained by a charge on the control grid which is negative with respect to the cathode. When the control grid is made sufficiently positive with respect to the cathode, the restraining force is removed and the tube conducts, at which time the control grid loses all control over the conduction of the tube which must be extinguished by reducing the potential of the anode to a point substantially equal to, or below the sustaining ionization potential. When the tube is thus extinguished the control grid resumescontrol over the conduction resistor 6 consitute a phase shifting combination as the speed of the engine is increased, the spark is automatically advanced. By properly proportioning the values of the capacitor 5 and the resistor 6, the spark may be timed to give maximum efficiency at all speeds of the engine.

By having a separate system for each spark gap of an internal combustion engine, the usual distributor may be eliminated. The desired firing order may be obtained by properly spacing and offsetting the permanent magnets, one of which is shown at I, about the periphery of the cam shaft, or by using a single magnet and distributing the coils radially around the cam shaft.

A preferred embodiment of my invention as applied to ignition systems contemplates the inclusion of the tube 8, the spark-gap [9, the transformer 9, the capacitor H, and the resistor I2, into a single compact unit enclosed in a shielding container, represented schematically on the drawin by the dotted line I l. The purpose of this arrangement is to eliminate the necessity for long high-tension leads and thus reduce to a minimum the extraneous oscillations that cause radio interference.

While I have shown and described my invention as applied to ignition systems for internal combustion engines, it is to be understood that, to those skilled in the art, other uses and applications of my invention and modifications thereof will be obvious without departing from the spirit and scope thereof. For example, it could be used as a means of stroboscopic excitation wherein the moving part to which the magnet is secured would be the part under observation.

What I claim is:

1. An ignition system for an engine having a cam shaft, comprising a source of electrical pulses including a permanent magnet secured to said cam shaft and a pick-up coil associated therewith, a pulse sharpening device connected to said coil, a discharge tube, said tube being triggered by said pulses, a series connected capacitor and resistor forming a phase shifting device responsive to changes in the frequency of said pulses connected intermediate said pulse sharpening device and said tube, a transformer having a primary and a secondary winding, the current in said primary winding being controlled by said tube, and a spark gap connected across said secondary winding.

'2. An ignition system for an engine having a cam shaft, comprising a source of electrical pulses synchronized with the rotation of said cam shaft, :1. pulse sharpening device connected to said source, a gas discharge tube, said tube being triggered by said pulses, a series connected capacitor and resistor forming a phase shifting device responsive to changes in the frequency of said pulses connected intermediate said pulse sharpening device and said tube, a transformer having a primary and a secondary winding, the current in said primary winding being controlled by said tube, and a spark gap connected across said secondary winding.

3. An ignition system for an engine having a cam shaft, comprising a source of electrical pulses synchronized with the rotation of said cam shaft, a gas discharge tube, said tube being triggered by said pulses, a series connected capacitor and resistor forming a phase shifting device responsive to changes in the frequency of said pulses connected intermediate said source and said tube, a transformer having a primary and a secondary winding, the current in said primary winding being controlled by said tube, and a spark gap connected across said secondary winding.

4. An electrical circuit for use in conjunction with a mechanism having a cyclically moving part comprising, a source of electrical pulses including a permanent magnet secured to said moving part, a pick-up coil associated therewith, a pulse sharpening device connected to said coil, a gas discharge tube, said tube being triggered by said pulses, a series connected capacitor and resistor forming a phase shifting device responsive to changes in the frequency of said pulses connected intermediate said pulse sharpening device and said gas discharge tube, and a load device, the current through said load device being controlled by said tube.

5. An electrical circuit for use in conjunction with a mechanism having a cyclically moving part comprising, a source of electrical pulses including a permanent magnet secured to said moving part, a pick-up coil associated therewith, a gas discharge tube, said gas discharge tube being triggered by said pulses, a series connected capacitor and resistor forming a phase shifting device responsive to changes in the frequency of said pulses connected intermediate said coil and said gas discharge tube, and a load device, the current through said load device being controlled by said tube.

6. An electrical circuit for use in conjunction with a mechanism having a cyclically moving part comprising, a source of electrical pulses synchronized with said cyclically moving part. a gas discharge tube, said tube being triggered by said pulses, a, series connected capacitor and resistor forming a phase shifting device responsive to changes in the frequency of said pulses connected intermediate said source and said tube, and a load device, the current through said load device being controlled by said tube.

7. An ignition system for an engine having a cam shaft, comprising a source of electrical pulses including a permanent magnet secured to said cam shaft and a pick-up coil associated therewith, a pulse sharpening device connected to said coil, a discharge tube having a cathode and a control grid, a capacitor connected between said pulse sharpening device and said control grid, a resistor shunting said control grid and said cathode. said caoacitor and said resistor forming a phase shifting device, a transformer having a primary and secondarv winding, the current in said primary winding being controlled by said tube, and a spark gap connected across said secondary winding.

8. An electrical circuit for use in conjunction with a mechanism having a cyclically moving part comprising, a. source of electrical pulses including a permanent magnet secured to said moving part, a pick-up coil associated therewith, a pulse sharpening device connected to said coil, a discharge tube having a cathode and control grid, a capacitor connected between said pulse sharpening device and said control grid, a resistor shunting said control grid and said cathode, said capacitor and said resistor forming a phase shifting device, a load device, the current through said load device being controlled by said tube.

9. An ignition system for an engine having a cam shaft, comprising a source of electrical pulses including a permanent magnet secured to said cam shaft and a pick-up coil associated therewith, a pulse sharpening device connected to said coil, a discharge tube, said tube being triggered by said pulses, an impedance network forming a phase shifting device responsive to changes in the frequency of said pulses connected intermediate said pulse sharpening device and said tube, a transformer having a primary and a secondary winding, the current in said primary winding being controlled by said tube, and a spark gap connected across said secondary winding.

10. An electrical circuit for use in conjunction with a mechanism having a cyclically moving part comprising, a source of electrical pulses including a permanent magnet secured to said moving part, a pick-up coil associated therewith, a gas discharge tube, said tube being triggered by said pulses, an impedance network forming a phase shifting device responsive to changes in the frequency of said pulses connected intermediate said coil and said tube, and a load device, the current through said load device being controlled by said tube.

GEORGE D. HANCHET'I, JR.

REFERENCES CITED The following references are of record in the 

